Charlotte Downie, 27, was putting a Little Angels nappy on her daughter Neve, aged two when the little girl screamed out in pain.
The tot told her mum ‘it’s sore’, and Charlotte was horrified to notice there was blood on the child.
She inspected the supermarket own-brand nappies and found a shard of glass inside.
Mum-of-two Charlotte has demanded an apology from Asda, where the nappies were bought from.
Charlotte, from Dumferline, Fife, said: “I put the nappy on and then I heard Neve screaming, she was saying, ‘it’s sore’.
“When I checked, I noticed that there was a scratch and blood coming off her.
“I looked in the nappy and that’s when I saw a clear bit of glass.”
Charlotte immediately contacted NHS 24, scared that her daughter could have an infection, and took her to the GP.
She added: “I can categorically say that the glass did not come from my home.
“I have a toddler and a 12-week-old in the house so I have no glass in the house.”
She called Asda customer services to complain but was horrified at the insinuation that she may have put the glass there herself.
Asda continues to insist that “a customer can have confidence that they are the first person to open their packet of nappies.”
An Asda spokesperson confirmed the company will investigate whether the source of the object is domestic or commercial.
Charlotte took the nappy back to the store in St Leonards, Dunfermline, where the pack was bought from.
She said: “I was told it would take 40 days to investigate.
“There doesn’t seem to me that there’s any urgency to deal with a serious issue.
“They haven’t taken the product off the shelves. I mean we’re not talking about a misshapen crisp here.
“When I was called the next day, they were very rude to me.
“They said they had no idea how that would happen because the nappies are made in a protective environment.
“What are they implying, that I would put glass in my daughter’s nappy?”
A spokesman for Asda said: “We are extremely proud of our Little Angels nappies so we take complaints of this nature very seriously and are sorry to hear of Ms Downie’s complaint.
“We have begun a full and thorough investigation to understand what happened but would like to reassure her and all our customers that we have stringent processes in place to ensure there is no contamination within this robust process.
“Our nappies are produced and packed on an enclosed line within a sealed environment and if the door of the production line is opened, the conveyor belt stops and any nappies on the line are rejected.
“This means a customer can have confidence that they are the first person to open their packet of nappies.”